Electric-motor control.



N0- 829,144. PATENTED AUG. 21 1906. M. W. DAY. ELECTRIC MOTOR CONTROL.

APPLICATION FILED JUNE 2 Inventor. Maxwell W. Day. by I Am;

Illlllllllhhllllll! UNITED STATES L PATENT OFFICE.

MAXWELL W. DAY, SOHENEUTADY, NEW YORK, ASSIGNOR 'TO GEN- ERAL ELE TRIO COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC-MOTOR CONTROL.

Specification of Letters Patent.

Patent-ed Aug. 21,1900.

To all whom it may concern.-

well as that of the generator. nor an efficient s ed control over wide Be it known that I, MAXWELL W. DAY, a citizen of the United States, re'siding at Schenectad county of Schenectady, State of New Yor have invented certain new and useful Improvements in Electric-Motor Control, of which the following is a specification.

My invention relates to the control of electric motors; and its object is to provide a novelarrangement of cut-out switches for a plurality of motors normally connected in series and controlled in speed by a single controlling-switch.

A systeni that is frequently employed for the control of motors where s ed controlby fine gradations and over wi e ranges is desired is known as the Ward Leonard'sys-.

tem. In'this system the motor to be controlled is supplied from a generator which is driven by any suitable source of power. The fields of both motor and'generator are separately excited, andthe field strength of the generator is controlled. greater range of s ed than the Leonard sys tem gives it has con customary heretofore to vary the strength of the motor-field as two motors are permanently connected in series, however, and one motor becomes disabled from any cause, it is necessary to cut it out of circuit and o crate by means of the remaining motor. on this. is done, the volt e impressed upon the remaining motor is twice as eat as when the, two motors were connects in series. The motor speed with the same field strength is consequentl doubled. Thus if the higher s eeds with t e motors in series were obtaine by weakenin the fields it is essential to prevent such wea ening when operating with a singlemotor only.

In order to obtain a In this man-.

By my invention I provide a novel arrangement of cut-out switches such that when one motor is cut out of circuit the speed-controlling switch is prevented from weakening the field of the remaining motor. Although I shall describe my invention as applied to the motors controlled the Ward Leonard's stem, modified to inc ude means for contro ling the field strength of the motors, it will be understood that m invention is not limited to motors control ed by this particular system,, but is applicable to the control of any motors which are normally connected in series and have their field strengths varied to obtain speed variation.

My invention will best be understood by reference to the accompanying drawings, III which. i I

Figure 1 shows diagrammatically my invention applied to two motors controlled in accordance with the Ward Leonard system, and Fig. 2 shows a detail of a cut-out switch. In the drawin s, G represents a generator which is driven om any suitable source of power and which supplies current to the armatures of the motors M M. The generator G is shown as a compound-wound machine with the series field g, which may or ma not be provided with the shunt g and the s ort circniting switch g, and the main field g, which is separate] excited from any suitable source, 'as in 'cated by the mains e e. The two motor-fields m m are also separately excited and in the drawings are shown ex' cited from the same source.

D represents the main controlling-switch.

B represents a blow-out coil for the con troller.

0 represents a circuit-breaker in the armsture-circuit.

A A represent cu t-out switches for the motor-armatures, and F F cut-out switches for the motor-field.

The controllin -switch D is arranged to open and close tfie armature-circuitan i to include variable portions of the resistance R in series with the generator-field or with the motor-fields. The controlling-switch D is also arranged with two sets of stationary contacts connected to the resistance R and displaced 'by one hundred and eighty de es, so that the switch may be rotated in either direction for the op of the motor an at the same time permit ite directions of rotation.

the use of all the contact-fingers. In the off position of switch D, as shown, the motor-armatures M M are connected in a closed circuit in series with each other and with the resistance 1", while the fields are connected with full strength to the source of excitation e (2. These circuits may be traced as follows: from the upper terminal of resistance r to contact (1", contact (1, switch A, motor-armature M, switch A, switch A, mo rarmature M, switch A, blow-out coil B, contact d, contact d, lower terminal of resistance 1'. The field-circuit is from line 6, switches F and F, and fields m and m in parallel, contact (1, contact (i to line 6. This connection of the motors, which is for braking, so as to bring the motors to rest immediately upon bringing switch D to its open position, is intended for use in the control of any motor-operated mechanism, such as a turret on a battle-ship, which should be stopped. at once upon cutting ofi the current from the motors. When switch D is moved in one direction or the other to start the motors, the armaturebraking circuit is broken either at contact d or contact (1", dependin upon the direction of movement of switch Assume that the movable contacts of switch D are moved toward the left to start the motors with a given direction of rotation. When the stationary contact-fingers engage the movable contacts on the dotted line 40, the following circuits are closed: from the left-hand brush of generator G, through circuit-breaker C, contact (2 to contact at, switch A, motor-armature M, switch A, switch A, motor-armature M, switch A, blow-out coil B, contact (i contact (1 through series field g, to right-hand brush of generator G. The two motor-armatures are thus connected in series with the armature of generator G, and this connection is maintained throughout the further movement of the controll1ng-switeh. The circuit of the motor-fields has already been traced. The circuit of the generatonfield is as follows: from line e, to the generator-field g, to lower terminal of resistance R, through the entire resistance, to contact-finger d, to contactfinger d, and to line-wire c. The generatorfield is thus connected to the source of excitation with all the resistance R in series therewith. As the motion of the movable contacts of switch 1) toward the right is continued a section of resistance R is short-circuited by means of contact-finger d. When the third position is reached, another section is short-clrcuited by contact-finger (I This short-circuiting of resistance R by sections is continued by the fingers of the two groups alternately until in position .21 the resistance R is entirely short-circuitcd and the generator G is operating with full field strength.

In passing from osition 21 to position .20 a comiection is esta llliilled between (1 and d thereby connecting the left-hand terminal of shown in detail in Fig. 2.

generator-field g to line-wire c inr'lcpcndently of the resistance it. At the same time the connection between lingers and (12 is broken, thereby breaking the connection be tween line-wire e and the left-hand terminals of motor-fields m and m. A second connection between these field-terminals and linewire e, however, remains through the resistance R, and since this resistance is entirel short-circuited in position 21 the motoreLds m and we still have full strength. As the movement is continued into position 18 the short circuit is removed from one section of resistance R by contact-finger ([13. In the next position a short circuit is rc moved from a second section by contactfinger d Thus the several sections are consecutively included in' series with the motor- The motor-fields are thereby weakened and the speed of the motors further increased. This weakening of the fields is limited by the contact at, which serves to maintain a ortion of resistance R short-circuited throng the remaining positions of switch D. In this way the fields are maintained with SllfTlGiGIlh strength for proper operation. It is evident, however, that if one of the motors is disabled and it is necessary to cut it out of circuit the armature of the other motor will be subjected to the full generator voltage, and consequently its speed with full field will be double its speed when the two motors are connected in series with full fields. Therefore the controlling-switch. should be prevented from weakening the field of the remaining motor after one is cut out. I accornplish this by the arrangcn'ient'ol the cut-out switches. Assume that one of the motors as, for instance, Mis injured. To cut it. out. switch A is thrown upward into en gagement with the contacts a and switch F is opened. It will be seen that the armature M is simply cut out of circuit, the circuit of the remamin r motor-armature being completed throng 1 the contacts a. The field m is also cutout of circuit by the opening of switch F. The opening of this latter switch permits the two spring-clipsj" to close. The arra ement of these spring-clips, which is indicated diagrammatically in Fig. 1, is When the switch F is closed, the insulating-wedgcffl carried by the handle of the switch, is pressed between the spring-clips f, holding them apart. When switch his opened, the clips f automaticallyspi'ing together. This closing of theclips connects line-wire (2 directly to the ITS left-hand terminals, of the motor-fields m and m.- Since the right-hand terminals of the far as the motor-field circuit is concerned. The resistances 1' are merely discharge resistances for the fields m m, and the resistances r are arranged to be inserted in the armature-circuit to reduce the current before opening the armature-circuit.

I have shown a complete system adapted for controlling a turret o erated by a plurality of motors on the Ward eonard system, and I have shown and described, for the sake of completeness, many features which form no part of my invention and which may be omitted or altered, as desired. Furthermore, the

form of interlock between the cut; out

switches and the speed-controlling switch may be varied without departing from the spirit of my invention. Accordingly I aim in the appended claims to cover all such modifications which are within tlfe scope of my invention.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In combination, two motors connected in series, a resistance adapted for connection in the field-circuit of said motors, a speedcontrolling switch adapted to connect varying portions of said resistance in the fieldcircuit, cut-out switches for said motors, and means for preventing said speed-controlling switch from connecting resistance in the field-circuit when one motor is cut out.

2. In combination, two motors connected in series, a speed-controlling switch adapted to vary the hold strength of said motors, cutout switches, and means for preventing said speed-controlling switch from weakening the hold of one motor when the other motor is cut out.

3. In combination, two motors connected in series, a speeil-controlling switch adapted to vary the hold strength of said motors, cutout switches, and means operatively connected to a cut-out switch for preventing said speed-controlling switch from weakening the field of one motor when the other motor is cut out.

4. In combination, two motors connected in series, a resistance in the field-circuit of said motors, a speed controlling switch adapted to short-circuit variable portions of said resistance, cut-out switches, and means inde endent of said speed-controllin switch for s lort-eircuiting said resistance w ien one motor is out out.

5. In combination, two motors connected. in series, a resistance in the field-circuit of said motors, a speed controlling switch ada ted to short-circuit variable portions of sai resistance, cut-out switches, and means operatively connected to a cut-out switch for short-circuiting said resistance when one motor is cut out.

6. In combination, two separately-excited motors connected in series, a resistance in the field-circuit of said motors, a speed-controlling switch ada ted to short-circuit variable portions of sai resistance, cut-out switches and means for connecting the field of one meter directly to the source of excitation independently of said resistance when the other motor is cut out.

7. In. combination, a separately excited generator, two separately-excited motors connected in series to said generator, a field resistance, a speed-controlling switch adapted to connect variable portions of said resistance in the field-circuit of the generator or of the motors, cut-out switches, and means for preventing said speed-controlling switch from connecting said resistance in the circuit of one motor-field when the other motor is cut out.

8. In combination, a separately-excitcil generator, two separately-(mited motors connected in :seric-s to said generator, a licld resistance, a speedwoiitrolling switch adapted to connect variz'iblc portions of said resistance in the liold-circuit of the generator or of the motors, cut-out switches and means opcrativoly connected to a cut-out switch for connecting, the iicld of one motor directly to the source of excitation indepcnllcntly of said SIHUlltt)llbl'i)lllllg switch when the other motor is cutout.

ln Witncss whereof I hereunto set my hand 5 this 25th day of June, 1904.

MAXWELL W. DAY. Witnesses BENJAMIN B. HULL, l IELEN Unrono. 

